Allow one-time randomization in field trials to work even if metrics are disabled.

chrome/browser/metrics/metrics_service.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 //------------------------------------------------------------------------------
 // Description of the life cycle of a instance of MetricsService.
 //
 //  OVERVIEW
 //
 // A MetricsService instance is typically created at application startup.  It
@@ skipping 461 matching lines @@
 void MetricsService::Stop() {
   HandleIdleSinceLastTransmission(false);
   SetReporting(false);
   SetRecording(false);
 }
 
 std::string MetricsService::GetClientId() {
   return client_id_;
 }
 
+std::string MetricsService::GetClientIdNonEmpty() {
+  PrefService* pref = g_browser_process->local_state();
+  DCHECK(pref);
+  std::string client_id = pref->GetString(prefs::kMetricsClientID);
+  if (client_id.empty()) {
+    client_id = GenerateClientID();
+    pref->SetString(prefs::kMetricsClientID, client_id);
+
+    // Might as well make a note of how long this ID has existed
+    pref->SetString(prefs::kMetricsClientIDTimestamp,
+                    base::Int64ToString(Time::Now().ToTimeT()));
+  }
+  return client_id;
+}
+
 void MetricsService::SetRecording(bool enabled) {
   DCHECK(IsSingleThreaded());
 
   if (enabled == recording_active_)
     return;
 
   if (enabled) {
     if (client_id_.empty()) {
-      PrefService* pref = g_browser_process->local_state();
-      DCHECK(pref);
-      client_id_ = pref->GetString(prefs::kMetricsClientID);
-      if (client_id_.empty()) {
-        client_id_ = GenerateClientID();
-        pref->SetString(prefs::kMetricsClientID, client_id_);
-
-        // Might as well make a note of how long this ID has existed
-        pref->SetString(prefs::kMetricsClientIDTimestamp,
-                        base::Int64ToString(Time::Now().ToTimeT()));
-      }
+      client_id_ = GetClientIdNonEmpty();
     }
     child_process_logging::SetClientId(client_id_);
     StartRecording();
 
     SetUpNotifications(&registrar_, this);
   } else {
     registrar_.RemoveAll();
     PushPendingLogsToUnsentLists();
     DCHECK(!pending_log());
     if (state_ > INITIAL_LOG_READY && unsent_logs())
@@ skipping 1180 matching lines @@
     thread_id = base::PlatformThread::CurrentId();
   return base::PlatformThread::CurrentId() == thread_id;
 }
 
 #if defined(OS_CHROMEOS)
 void MetricsService::StartExternalMetrics() {
   external_metrics_ = new chromeos::ExternalMetrics;
   external_metrics_->Start();
 }
 #endif